Building FX3-Compatible fxload for QHY USB3 Cameras

The standard fxload package provided by Debian and Ubuntu repositories only supports Cypress EZ-USB FX and FX2 (USB 2.0) microcontrollers. Many modern astronomical cameras—specifically QHY USB 3.0 models such as the QHY5III series—utilize the Cypress EZ-USB FX3 (CYUSB3014) controller.

Without FX3 firmware loading capability, these cameras remain stuck in bootloader state (Cypress WestBridge) upon connection and are not recognized by the indi_qhy_ccd driver.

---

1. Prerequisites and Compilation

Compile the updated fxload tool from the official libusb source repository:

# Install compilation prerequisites
sudo apt-get update
sudo apt-get install -y automake libtool libudev-dev build-essential git

# Clone libusb and compile with local prefix
git clone https://github.com/libusb/libusb.git /tmp/libusb
cd /tmp/libusb

./autogen.sh
./configure --prefix=/usr/local
make -j$(nproc)
sudo make install

# Compile the fxload utility included in libusb examples
cd examples
make fxload

# Install fxload into /usr/local/sbin
sudo install -o root -g root -m 755 .libs/fxload /usr/local/sbin/fxload

---

2. Identify the Cypress Bootloader Device

Execute lsusb to verify that the camera is in Cypress bootloader mode:

lsusb

Example output:

Bus 002 Device 003: ID 1618:0485 Cypress WestBridge

• Vendor ID: 1618 (QHYCCD)
• Product ID: 0485 (Cypress FX3 Bootloader)

---

3. Firmware Verification

Firmware binary images are typically bundled in /lib/firmware/qhy/ (installed with QHY INDI drivers or qhyccd libraries). Identify the exact .img file matching your camera model (e.g., /lib/firmware/qhy/QHY5III485.img).

Test loading manually:

sudo LD_LIBRARY_PATH=/usr/local/lib /usr/local/sbin/fxload -t fx3 -I /lib/firmware/qhy/QHY5III485.img -d 1618:0485

Expected output:

microcontroller type: fx3
/lib/firmware/qhy/QHY5III485.img: type Cypress IMG format
open firmware image /lib/firmware/qhy/QHY5III485.img for RAM upload
normal FW binary executable image with checksum
FX3 bootloader version: 0x000000A9
writing image...
transfer execution to Program Entry at 0x40014984

Following execution, the device will re-enumerate on the USB bus with its operational QHY vendor and product IDs.

---

4. Automated Udev Rule Configuration

To automate firmware upload whenever the camera is attached or powered on:

Create /etc/udev/rules.d/99-qhyccd_custom.rules:

sudo tee /etc/udev/rules.d/99-qhyccd_custom.rules <<'EOF'
ACTION!="add", GOTO="qhy_end_new"
SUBSYSTEM!="usb", GOTO="qhy_end_new"

# Trigger FX3 firmware upload upon detection of the WestBridge bootloader
ATTRS{idVendor}=="1618", ATTRS{idProduct}=="0485", ENV{LD_LIBRARY_PATH}="/usr/local/lib", RUN+="/usr/local/sbin/fxload -t fx3 -I /lib/firmware/qhy/QHY5III485.img -d 1618:0485"

# Grant standard user read/write access to QHY USB devices
ATTRS{idVendor}=="1618", MODE="0666"

LABEL="qhy_end_new"
EOF

[!IMPORTANT] Replace /lib/firmware/qhy/QHY5III485.img with the exact firmware filename corresponding to your specific camera model.

Reload udev rules:

sudo udevadm control --reload-rules
sudo udevadm trigger